To make 50 gallons of bordeaux mixture, proceed as follows: (1) Pulverize 5 pounds of copper sulfate (blue vitriol), place in a glass, wooden, or brass vessel, and add two or three gallons of hot water. In another vessel slake 5 pounds of quicklime in a small amount of water. When the copper sulfate is all dissolved, pour into a barrel and add water to make 40 or 45 gallons. Now strain the lime into this, using a sieve 50 meshes to the inch or a piece of cheese-cloth supported by ordinary screening. Stir thoroughly, and add water to the 50-gallon mark. The flocculent substance which settles is the effective fungicide. Always stir vigorously before filling the sprayer. Never add the strong lime to strong vitriol. Always add a large amount of water to one or the other first. Blue vitriol used alone would not only wash off quickly in a rain, but cause a severe burning of fruit and foliage. Lime is added to neutralize this burning effect of the copper. If the lime were absolutely pure only slightly more than one pound would be required to neutralize this burning effect. For many purposes an excess of lime is not objectionable and may be desirable. For nearly ripe fruit and ornamentals an excess of lime augments spotting. In such cases the least amount of lime possible should be used. Determine this by applying the cyanide test (2).
(2) Secure from the druggist 10 cents' worth of potassium ferrocyanide (yellow prussiate of potash) and dissolve it in water in an 8-ounce bottle. Cut a V-shaped slit in one side of the cork, so that a few drops of the liquid can be obtained. Now proceed as before. Add lime with constant stirring until a drop of the ferrocyanide ceases to give a reddish-brown color.
(3) When bordeaux mixture is desired in large quantities, stock solutions should be made. Place 100 pounds of copper sulfate in a bag of coffee-sacking, and suspend in the top of a 50-gallon barrel, and add water to the 50-gallon mark. In twelve to fifteen hours the vitriol will be dissolved and each gallon of solution will contain 2 pounds of copper sulfate. Slake a barrel of lime, and store in a tight barrel, keeping it covered with water. Lime so treated will keep all summer. It is really hydrated lime. This is often dried, pulverized, and offered on the market in paper bags of 40 pounds, each, under such names as ground lime, prepared lime, hydrated lime, etc. If the paper is not broken, the lime does not air-slake for a long time. One and one third pounds of hydrated lime equals in value one pound of quicklime. Air slaked lime cannot be used in preparing bordeaux mixture.
Arsenical poisons can be combined with bordeaux mixture. See Chapter XVII, page 290.
Ammoniacal copper carbonate. - For use on nearly mature fruit and on ornamentals. Does not discolor. Weigh out 3 ounces of copper carbonate, and make a thick paste with water in a wooden pail. Measure 5 pints of strong ammonia (26° Beaume) and dilute with three or four parts of water. Add ammonia to the paste, and stir. This makes a deep blue solution. Add water to make 50 gallons.
Copper carbonate. — For use in the above formula, it may be obtained as a green powder, or may be prepared as follows: Dissolve 12 pounds of copper sulfate in 12 gallons of water in a barrel. Dissolve 15 pounds of sal soda in 15 gallons of water (preferably hot). Allow the solution to cool; then add the sal soda solution to the copper sulfate solution, pouring slowly in order to prevent the mixture from working up and running over. A fine precipitate is formed which will settle to the bottom if allowed to stand over night. Siphon off the clear liquid. Wash the precipitate by adding clear water, stirring, and allowing to settle. Siphon off the clear water, strain the precipitate through muslin, and allow it to dry. This is copper carbonate. The above amounts will make about 6 pounds.
Copper sulfate. — See Sulfate of Copper, p. 258.